I have an application that uses a static class to store settings:
namespace ABC
{
public static class MS
{
public static bool abc;
public static bool def;
...
}
}
When the app starts up it goes to the database and updates some of these settings.
I have been told that holding them in a static class is not ideal for when I am doing bindings and adding notification so I'm thinking I should new a class and the hold them in an instance. If that's the case can someone give me some advice. Should I do that when the application starts up and should it be in the constructor of the App() if that is the best way to do it then how can I do this. Any small 4-5 line example would be a big help
public partial class App : Application
{
public static xxx
public App()
{
AS.appUpdated = "Feb 1, 2017";
AS.appVersion = "0.1";
InitializeComponent();
MainPage = new MS.MainPage();
}
}
Have a look at James Montemagno's settings plugin.
https://github.com/jamesmontemagno/SettingsPlugin
This abstracts away a lot of the plumbing around settings and persisting them locally. Calling one of your settings from anywhere in your application then becomes as simple as calling Settings.MySettingName.
When it comes to binding these values to a view I would always create a property for them in your view model that simply returns the value from the settings. If need be you can put them in a base viewmodel and go from there.
public class MyViewModel : BaseViewModel
{
}
public class BaseViewModel
{
public bool SettingA => Settings.SettingA;
public bool SettingB => Settings.SettingB;
}
Related
I have an application that I am working on. The call to the data manager to set up looks like this:
public partial class App : Application
{
public App()
{
InitializeComponent();
MainPage = new Japanese.MainPage();
}
public static DataManager DB
{
get
{
if (AS.dm == null)
{
AS.dm = new DataManager();
}
return AS.dm;
}
}
protected override void OnStart()
{
AS.GetSettings();
AS.selectedPhraseCount = AS.dm.GetTotalPhrasesCountForSelectedCategories();
}
In other words the datamanager is set up when it's first needed.
Can someone tell me if there is any advantage to doing this. It would seem to me to be simpler just to do a call to AS.dm = new DataManager() in the onStart event.
public partial class DataManager
{
protected static object locker = new object();
protected SQLiteConnection db1;
protected SQLiteConnection db2;
public DataManager()
{
db1 = DependencyService.Get<ISQLiteDB1>().GetConnection();
db2 = DependencyService.Get<ISQLiteDB2>().GetConnection();
You'd need to post a bit more code (for example where are dm and AS declared?) to be absolutely sure, but this method of having a static declaration with a private constructor is called the Singleton pattern and is designed to ensure that only one instance of the object (in your case the DataManager) can ever exist.
See this existing question
However, your code looks slightly odd in the OnStart because it looks like you are referencing the datamanager using the dm backing variable rather than the DM property.
I am kinda unclear on how to pass data to other views. I gathered there are 3 ways to do this but I not sure how to do 2 of them.
Send data through messenger(not sure if you can send objects otherwise I can see thing getting pretty messy if you have to send like 10 pieces of data or something like that along).
Somehow pass the data through the constructor of the new view model. I say "somehow" as I am unclear how to do that when using an IOC container(in this case the built in one).
Passing the data through a parameter. I seen a couple of tutorials that show you how to do navigation for the windows phone but none really talk about parameter passing. I am guessing this would still be an option.
From what I heard is that Option 1 is sort of the old way of doing it. Option 2 seems to be a newer way and better way to do it but I cannot find any examples on people showing how to do it.
I don't know how to do it because the Ioc should be creating the instance of the view so how do you pass in data into it when that data does not exist?
The two main ways I do this is:
1)Use the messenger:
Sender class:
public class TrafficLight
{
public string Color{get;set;}
public TimeSpand Duration{get;set;}
}
public class TrafficLightService
{
public void SendLight(TrafficLight light)
{
Messenger.Default.Send(light);
}
}
Receiver:
public class MyViewModel
{
public MyViewModel()
{
Messenger.Default.Register<TrafficLight>(DoSomethingWithTrafficLight);
}
private void DoSomethingWithTrafficLight(TrafficLight light)
{
}
}
What happens here is that the source object is using the Messenger as an event broker. Object A doesn't need to know about object B, they just both need to know about the messenger.
2)
Just use dependency injection:
public class TrafficLight
{
public string Color{get;set;}
public TimeSpand Duration{get;set;}
}
public class LightEventArgs:EventArgs
{
public LightEventArgs(TrafficLight light)
{
_light=light;
}
public TrafficLight Light{get{return _light;}}
}
public interface ITrafficLightService
{
void SendLight(TrafficLight light);
public event EventHandler<LightEventArgs> TrafficLightSet;
}
public class TrafficLightService
{
public void SendLight(TrafficLight light)
{
Messenger.Default.Send(light);
}
public event EventHandler<LightEventArgs> TrafficLightSet;
}
public class TrafficLightSenderViewModel
{
public TrafficLightSenderViewModel(ITrafficLightService trafficLightService)
{
_trafficLightService=trafficLightService;
_trafficLightService.Send(new TrafficLight{Color="Red"});
}
}
public class TrafficLightReceiverViewModel
{
public TrafficLightReceiverViewModel(ITrafficLightService trafficLightService)
{
_trafficLightService=trafficLightService;
_trafficLightService.TrafficLightSet+= TrafficLightNotification;
}
private void TrafficLightNotification(TrafficLightEventArgs args)
{
DoSomethingWithTheLight(args.Light);
}
}
public class ViewModelLocator
{
public ViewModelLocator()
{
ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);
if (ViewModelBase.IsInDesignModeStatic)
{
SimpleIoc.Default.Register<ITrafficLightService, Design.TrafficLightService>();
}
else
{
SimpleIoc.Default.Register<ITrafficLightService, TrafficLightService>();
}
SimpleIoc.Default.Register<TrafficLightSenderViewModel>();
SimpleIoc.Default.Register<TrafficLightReceiverViewModel>();
}
public MainViewModel Sender
{
get { return SimpleIoc.Default.GetInstance<TrafficLightSenderViewModel>(); }
}
public MainViewModel Receiver
{
get { return SimpleIoc.Default.GetInstance<TrafficLightReceiverViewModel>(); }
}
}
This is a bigger example and more complex.
Lets walk through this step by step:
In MVVM Light we use the ViewModelLocator for 2 things: 1)To register all our viewmodels and services.
Provide a way to allow the View to get a viewmodel in XAML
When we try to resolve a ViewModel
SimpleIoc.Default.GetInstance<TrafficLightReceiverViewModel>();
SimpleIoc looks at whether the viewmodel has any dependencies. In our case we do, we need an ITrafficLightService for both our viewmodels. What happens is that SimpleIoc sees if it can resolve that class and, in the process, checks to see if ITrafficLightService has any dependencies that need resolving as well. If SimpleIoc can resolve the chain of dependencies required to instantiate your viewmodel it does so and then hands back a fully built object.
I have a Page which consist of AddPage.xaml and AddPage.xaml.cs. I want to create a generic class AddPage which extends from PhoneApplicationPage to outsource some repetitive code like Save or Cancel.
If I change the base class from PhoneApplicationPage to my new generic class, I get this error: Partial declarations of 'AddPage' must not specify different base classes.
To accomplish this you need to do the following.
First, create your base class
public class SaveCancelPhoneApplicationPage : PhoneApplicationPage
{
protected void Save() { ... }
protected void Cancel() { ... }
}
Then, your AddPage needs to be modified to inherit from the base class. The main places this is needed is within the code (AddPage.xaml.cs) AND within the xaml
Code:
public partial class AddPage : SaveCancelPhoneApplicationPage { ... }
Xaml:
<local:SaveCancelPhoneApplicationPage
x:Class="MyPhone.Namespace.AddPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MyPhone.Namespace"
<!-- other xaml elements -->
</local:SaveCancelPhoneApplicationPage>
UPDATE: Info added based on comments
If you need to have generic like functionality and you must use the Page to do this (rather than a ViewModel) then you can still do this using generic methods
public abstract class SaveCancelPhoneApplicationPage : PhoneApplicationPage
{
protected override void OnNavigatedTo(blaa,blaa)
{
var obj = CreateMyObject();
obj.DoStuff();
}
// You should know what your objects are,
// don't make it usable by every phone dev out there
protected MyBaseObject MyObject { get; set; }
protected T GetMyObject<T>() where T : MyBaseObject
{
return MyObject as T;
}
}
public class AddPage : SaveCancelPhoneApplicationPage
{
public AddPage()
{
MyObject = new MyAddObject();
}
}
In order to outsource some functions you just declare some add class which does the common work. Having another page doesn't do that work.
public class Add
{
public bool SaveContent(string filename, string content)
{
....//some content
return true;
}
public string ViewContent(string filename)
{
string content="";
.....
return content;
}
}
Add this part of code where you thought it is redundant.
Add obj=new Add();
obj.SaveContent("myfile.txt","Hello.This is my content.");
string content("myfile.txt");
Tell me if this is what you intend or not.
I created a web application using ASP.Net MVC 3 and EF 4.1, and I am using the UnitOfWork pattern, but nothing is getting committed to the database. All this is quite new to me, and I don't know where to start to resolve this issue.
I based myself on this post to create my web application:
http://weblogs.asp.net/shijuvarghese/archive/2011/01/06/developing-web-apps-using-asp-net-mvc-3-razor-and-ef-code-first-part-1.aspx
The final code, which can be obtained here also has a service layer and the UnitOfWOrk is being injected into the services.
Instead of using the custom injector based on Unity 2 as they are in that project, I am using Unity.Mvc3.
Here is my IUnitOfWork class:
public interface IUnitOfWork
{
void Commit();
}
And here is my UnitOfWork class:
public class UnitOfWork : IUnitOfWork
{
private readonly IDatabaseFactory databaseFactory;
private MyProjectContext dataContext;
public UnitOfWork(IDatabaseFactory databaseFactory)
{
this.databaseFactory = databaseFactory;
}
protected MyProjectContext DataContext
{
get { return dataContext ?? (dataContext = databaseFactory.Get()); }
}
public void Commit()
{
DataContext.Commit();
}
}
And here is how one of my service class look like:
public class RegionService : IRegionService
{
private readonly IRegionRepository regionRepository;
private readonly IUnitOfWork unitOfWork;
public RegionService(IRegionRepository regionRepository, IUnitOfWork unitOfWork)
{
this.regionRepository = regionRepository;
this.unitOfWork = unitOfWork;
}
...
}
At start-up, my UnitOfWork component is being registered like this:
container.RegisterType<IUnitOfWork, UnitOfWork>();
Now, no matter whether I try to insert, update or delete, no request is being sent to the database. What am my missing here?
UPDATE:
Here is the content of DataContext.Commit():
public class MyProjectContext : DbContext
{
public DbSet<Region> Regions { get; set; }
public virtual void Commit()
{
base.SaveChanges();
}
}
And here is databaseFactory.Get():
public interface IDatabaseFactory : IDisposable
{
MyProjectContext Get();
}
UPDATE #2:
Using the debugger, I am noticing that my Region service and controller constructors are getting called once when performing only a select, but they are called twice when performing an update. Is this normal?
Ok, I found the culprit. It has to do with how I was registering my database factory.
Instead of
container.RegisterType<IDatabaseFactory, DatabaseFactory>();
I needed
container.RegisterType<IDatabaseFactory, DatabaseFactory>(new HierarchicalLifetimeManager());
I found the information on this web site:
http://www.devtrends.co.uk/blog/introducing-the-unity.mvc3-nuget-package-to-reconcile-mvc3-unity-and-idisposable
That's an awfully complex implementation of Unit of Work. I actually prefer this one:
http://azurecoding.net/blogs/brownie/archive/2010/09/22/irepository-lt-t-gt-and-iunitofwork.aspx
Much simpler, and much more flexible. Although you do have to work out a few things for yourself.
May just be a typo but in UnitOfWork your private MyProjectContext is called dataContext (lowercase d)
But in your commit method your calling DataContext.Commit. Any chance that's actually calling a static method that you didn't intend to call? More likely a typo but thought I'd point it out.
+1 for an overly complex implementation of UnitOfWork.
I am creating an application in mvc3 and wondering how to deal with database data which is required for all application requests, some of them depends on a session, some of them depends on url pattern basically all data is in database.
Like to know best practice
What I do in my applications and consider to be the best practice is to load your common data to the ViewBag on the Controller constructor.
For every project, I have a DefaultController abstract class that extends Controller. So, every controller in the project must inherit from DefaultController, instead of Controller. In that class' constructor, I load all data common to the whole project, like so:
// DefaultController.cs
public abstract class DefaultController : Controller
{
protected IRepository Repo { get; private set; }
protected DefaultController(IRepository repo)
{
Repo = repo;
ViewBag.CurrentUser = GetLoggedInUser();
}
protected User GetLoggedInUser()
{
// your logic for retrieving the data here
}
}
// HomeController.cs
public class HomeController : DefaultController
{
public HomeController(IRepository repo) : base(repo)
{
}
// ... your action methods
}
That way you will always have the logged in user available in your views.
I do the same as #rdumont but with one exception: I create a CommonViewModel which I use to define all common properties that I use.
public class CommonViewModel
{
public string UserName {get;set;}
public string Extension {get;set; }
}
Declare a property in the base controller:
public abstract class BaseController : Controller
{
protected CommonViewModel Commons { get; private set; }
protected virtual void OnResultExecuting(ResultExecutingContext filterContext)
{
ViewBag.Commons = Commons;
}
}
By doing so I get everything almost typed. The only cast that I need to do is to cast ViewBag.Commons to the CommonViewModel.
Best is to avoid ViewBag at all.
See this answer, which details how to use Html.RenderAction() for that purpose:
Best way to show account information in layout file in MVC3
I'd suggest using a base ViewModel class.
So a base class with properties/functions which should be available at any point.